Kerf-cutting machine



W 9 W49. L. 0. HAGENBOOK 2,478,389

KERFCUTTING MACHINE Filed Dec. 8, 1945 8 Sheets-Sheet l INVENTOR l fiflagmoo! @6246 M A T TOQN raw Aug Q, W49. L. D. HAGENBOOK -KERF-CUTTING MACHINE 8 Sheets-Sheet 2 Filed Dec. 8, 1945 i flag 0 ATTORNEY Aug. 9, 1949. Y L. D. HAGENBOOK 2,478,339

KERF-CUTTING MACHINE Filed Dec. 8, 1945 8 Sheets-Sheet 5 Arron/vs) 9, 11949. 1.. D. HAGENBOOK 294789389 KERF-CUTTING MACHINE Filed Dec. 8, 1945 8 Sheets-Sheet 4 1949. o. HAGENBOOK v 2,478,389

KERF- CUTTING MACHINE Filed Dec. 8; 1945 8 Shee'ts-Sheet 5 62 I fif/ wbook 79 69 W 1 AT TOIQI EY 111 g, 1949. L. D. HAGENBOOK 2,478,389

KERF-CUT'I'ING MACHINE 8 Sheets-$heet 7 Filed Dec. 8, 1945 5i 9- a MEI/9% Aug. 9, 1949.. L. D. HAGENBOOIK 294739339 KERF-CUTTING MACHINE 8 Sheets-Sheet 8 Filed Dec. 8, 1945 BRA cYL i 203 agen om 23 227 x M i ,4rrORA/E y Patented Aug. 9, 1949 2,478,389 KEEP-CUTTING MACHINE Loy D. Hagenbook, Chicago, Ill., assignor to Goodman Manufacturing Company, Chicago, 111., a corporation of Illinois Application December 8, 1945, Serial No. 633,580

28 Claims. 1

This invention relates to improvements in kerfcutting machines, and more particularly relates to an improved mobile support mounting for a kerf-cutting machine of the type which is ordinarily mounted for movement along mine tracks and affording a means for moving the machine along the ground and sumping its cutter bar into or withdrawing it from a coal face.

This application is a continuation in part of my application Serial No. 556,309, filed September 29, 1944, now abandoned.

Keri-cutting machines of the type adapted to out along the ground or at various elevations with respect thereto have heretofore been mounted on continuous traction tread devices for travel along the mine bottom. These tread devices have also been used to sump the cutter bar of the machine into the coal face so it may be fed transversely across the coal face by the turntable of the cutting machine. The same types of cutting machines have also been mounted on rubber tired wheels.

In order to properly support the machine with its overhanging cutter bar and give it stability during cutting, the tread devices must be relatively long. This makes it diflicult to maneuver the machine, especially in confined spaces, and also results in tearing up the mine bottom, which is undesirable, especially close to the Working face, where the torn up bottom becomes mixed with the mined coal and must either be cleaned from the coal at the face or at the tipple outside of the mine.

Where rubber tires are used to support the machine, it is difiicult to maintain the cutter bar in a uniform cutting plane, especially when it is swung at an angle towards one side of the machine or the other, resulting in the depressing of the pneumatic tires on that side of the machine. This cannot ordinarily be corrected by tilting the machine to level the cutter bar and restricts the arc of movement of the cutter bar so that it cannot cut when moved beyond the limits of the rubber tire mounted wheels. The wheels and tires must also be of a relatively small diameter in order not to increase the height of the machine over the height of the same type of machine mounted on track wheels and rails, making it difiicult for the machine to have sufllcient tractive effort to sump the cutter bar by tractive effort of the rubber tired wheels and to travel about a rough or soft mine bottom.

The device of my present invention has as its objects to remedy these difficulties by mounting a mobile kerf-cutting machine of the type which is normally mounted on rails, on relatively short power driven laterally spaced continuous tread devices at its forward end, and on rubber-tired steering wheels at its rear end, and in so locating said wheels and continuous tread devices with respect to the center of gravity of the machine that the major portion of the loads will be taken on the relatively stable-continuous tread devices and the loads on the rubber-tired steering wheels will only be sufiicient to assist the tread devices in steering the machine.

Another object of my invention is to provide an improved support mounting for the machine on rubber-tired steering wheels and on power driven laterally spaced continuous tread devices, with a simplified and novel means for tilting the machine frame with respect to the tread devices by power, to maintain the cutter bar in the desired cutting plane.

. Still another object of my invention is to provide a kerf-cutting machine mounted on front laterally spaced continuous tread devices and rear rubber tired steering wheels, with an improved drive for the tread devices including means for applyin braking pressures to either tread device during operation of the rear steering wheels, for steering the machine, which pressures increase as the angle of turning of the rear steering wheels from the longitudinal axis of the machine increases.

A further object of my invention is to provide a novel form of power booster means for turning the rear steering wheels, for steering the vehicle.

A still further object of my invention is to provide an improved form of fluid operated booster means for turning the rear steering wheels, for steering the vehicle, together with braking means for the traction devices, operated by the steering means, which is so arranged as to apply the braking means to either traction device depending upon the direction of turning movement of the steering means, and which is also so arranged as to permit the braking means to be applied to each traction device when desired, to

hold the machine from movement regardless of the position of the steering means.

These and other objects of my invention will appear from time to time as the following specification proceeds and with reference to the accompanying drawings wherein: i

Figure 1 is a plan view of a Keri-cutting machine constructed in accordance with my invention;

Figure 2 is a view in side elevation of the machine shown in Figure 1;

Figure 3 is an enlarged detail plan view of the front part of the machine shown in Figure 1, with certain parts removed and with certain other parts broken away and shown in horizontal section, in order to show certain details of the drive to the laterally spaced continuous tread devices;

Figure 4 is a fragmentary sectional view taken substantially along line 44 of Figure 3;

Figure 5 is a transverse sectional view taken substantially along line 5-5 of Figure 3;

Figure 6 is a partial fragmentary sectional view taken substantially along line 66 of Figure 3, but showing the rear part of the kerf-cutting machine and its mounting on the machine in full;

Figure 7 is an enlarged detail fragmentary plan view of the forward part of the machine, with parts broken away and in section in order to show certain details of construction of one of the continuous tread devices and its mounting on the machine frame;

Figure 8 is a partial fragmentary sectional view taken substantially along line 88 of Figure 7 Figure 9 is a fragmentary end view, showing certain details of one of the continuous tread devices;

Figure 10 is a partial fragmentary transverse sectional view taken substantially along line l0lll of Figure 7;

Figure 11 is an enlarged detail view with certain parts shown in longitudinal section, in order to show certain details of the braking means for one of the continuous tread devices;

Figure 12 is an enlarged detail view in side elevation, with certain parts broken away and certain other parts shown in substantially longitudinal section, showing certain details of the mounting of the machine frame on the rear steer-- ing wheels;

Figure 13 is an end view of the rear steering wheels, with certain parts shown in transverse section in order to show certain other details of the mounting of the machine frame on the steering wheels, which are not shown in Figure 12;

Figure 14 is an enlarged detail fragmentary plan, view with certain parts shown in horizontal section, in order to show certain details of the means for turning the steering wheels;

Figure 15 is an enlarged detail plan view of the 1 steering mechanism, with certain other parts broken away and shown in horizontal section than in Figure 14, in order to show certain details thereof which are not shown in Figure 14; Figure 16 is an enlarged detail sectional view taken through the booster valve for the steering mechanism;

Figure 17 is an enlarged detail plan view showing certain other details of the steering mechanism, which are not shown in Figures 14, 15 and 16;

Figure 18 is an enlarged detail view with certain parts broken away and certain other parts shown in horizontal section, in order to show certain details of one of the valves for controlling braking of the continuous tread devices;

Figure 19 is a detail end view of the valve mechanism, for controlling braking of the continuous tread devices, with certain parts of the mechanism for operating the valves shown in transverse section;

Figure 20 is a fragmentary longitudinal sectional view taken substantially along line 20-20 of Figure 17; and

Figure 21 is a fluid diagram showing the fluid pressure circuit for the machine.

Referring now to the details of the embodiment of my invention illustrated in the several figures of the drawings, the same is shown as applied to a mounted kerf-cutting machine of a conventional form, which has heretofore been mounted on track wheels for propulsion and guiding the machine on, track rails during transportation of the machine, and during cutting. Such machines are well known so a detailed description thereof need not be made herein excepting to point out the principal elements and particularly those parts which are involved in the application of my invention thereto.

The machine shown in the drawings includes a main frame l0 having a turntable I! mounted at its forward end, which has a cutting element l2 mounted thereon and projecting forwardly therefrom. Said cutting element is herein shown as being trunnioned on trunnion supports 13, I3 mounted on the upper side of said turntable and projecting forwardly therefrom, to permit adjustment of said cutting element about a transverse axis. Said cutting element includes a frame I projecting from the forward end of said truck and having guides l5, l5 dependin therefrom. Said guides form a guiding means for a cutter bar support frame I6, which has a cutter bar I! projecting therefrom, having the usual cutter chain 18 movable thereabout. Adjustment of said outter bar towards or from said frame 14 is effected by means of a screw device I9, by mechanism driven from a motor 20 at the rear end of said cutting element, which motor also serves to drive said cutter chain about said cutter bar. The cutter chain drive mechanism and the drive connection from said motor to vertically adjust said cutter bar are not herein shown since they are well known to those skilled in the art and are no part of my present invention.

The turntable l I is turned by power by a motor 2| mounted on the main frame I0 rearwardly of the cutting element and operatively connected to said turntable as usual through a train of gears disposed rearwardly of the latter and not herein shown or described since it is no part of my present invention. Said motor also provides power for driving a pair of laterally spaced continuous tread devices 22, 22, for supporting the forward end of said main frame. The rear end of said main frame is supported on a pair of rubber-tired steering wheels 23, 23 in a manner which will hereinafter more clearly appear as this specification proceeds.

Referring now to the novel form of support mounting for the main frame on the laterally spaced continuous tread devices 22, 22, said tread devices may be of any well known form including a plurality of links in the form of ground engaging treads 25, 25, which are pivotally connected together by pins 26, 26, to form a continuous flexible chain. Said tread devices are mounted on a tread frame 21 on a rear idler sprocket 29, a central idler roller 30, and a forward drive sprocket 3| (see Figure 7). Said tread frame is in turn pivotally mounted on a pivoted arm 33, on a shaft 34, mounted at its inner end on said pivoted arm and projecting outwardly therefrom (see Figures 7 and 8). Said shaft is journaled in opposite sides of said tread frame on spaced radial thrust bearings 35, 35. The central idler roller 30 is journaled on said shaft on radial thrust bearings 36, 36.

Movement of said tread frame and continuous tread devices about the axis of the shaft 34 in one direction or another, is limited by a pair of vertically spaced lugs 39, 39 projecting inwardly from said tread supporting frame and adapted to engage a lug 40 projecting outwardly from the pivoted arm 33 and spaced between said lugs 39, 39. A lug 4| projecting inwardly from the forward end of said tread frame is adapted to have slidable engagement with a lug 42, projecting outwardly from said pivoted arm and forming a guide means for said tread supporting frame to hold said supporting frame-from twisting inwardly towards said pivoted arm.

It will be observed that each of the two endless tread devices 22 is made as short as structural requirements permit for a tread assembly of the kind shown, including the drive sprocket 29, the end idler 3|, and the intermediate idler 30 mounted between said drive sprocket and end idler concentric with the shaft 34 forming a pivotal bearing support for the tread frame 21 and permitting tilting of said tread frame relative to the support arm 33. For compactness, said drive sprocket and idlers arearranged as closely together as possible, leaving spaces for narrow cross connecting webs 28, 28 of the tread frame 21 between them, as clearly seen in Figure '7. Also the diameters of the drive sprocket 23 and idlers 30 and 3| are considerably less than the distance from the ground to the bottom of said turntable, so as to permit a wide range of tilting movement of said turntable and main frame, without interfering with said tread devices.

The tread devices 22 are thus very short compared with the length of the machine, and particularly with reference to the wheel base or supporting base established by said tread devices and the rubber-tired steering wheels 23 at the rear of the machine.

In the preferred form shown, the center of gravity of the machine is substantially at the center of the turntable II and rearwardly of the transverse pivotal mountings of the tread devices on the main frame l0, but is within the limits of said tread devices. The rubber-tired steering wheels 23- are spaced a substantial distance rearwardly of the center of gravity of the machine and of said tread devices 22, so that a greater portion of the loads during cutting and transportation will be taken on said continuous tread devices and the loads on said steering wheels will only be sufficient to give said steering wheels traction to assist said tread devices in steering the machine.

It should here be noted that the portion of the frame l4 projecting from the forward end of the truck, along with its depending guides and the cutter bar 1! and cutter chain 3 form a heavy overhanging weight in front of said tread devices, disposed in planes intersecting said tread devices and movable across the front of and to either side of said tread devices. The distance from the centers of the shafts 34, 34, forming transverse pivotal mountings for said tread devices on the main frame to the forward ends of said continuous tread devices, is less than the distance from the center of gravity of the machine to the rear end of said overhanging cutter chain, by a distance that prevents said overhanging weight from tilting the machine about said tread devices, but will still place only enough weight on the steering wheel tires to permit said Wheels to assist said tread devices in steering,

without loading the tires of said steering wheels beyond their normal rated loads.

The relatively short tread devices herein disclosed thus produce extremely high unit pressures between said tread devices and the ground, greatly in excess of unit pressures heretofore employed with any endless tread devices with which I am familiar. Yet I find that this arrangement affords the desired lateral stability for the machine while cutting, and at the same time permits ready maneuverability of relatively massive kerf-cutting machines of the kind herein contemplated, without excessive digging or tearing up of the mine bottom during travel of the machine, both during cutting and travel from place to place in the mine.

The rear idler sprocket 29 is mounted on a dead shaft 44 on radial thrust bearings 45, 45 (see Figure 7). Said idler shaft is slidably mounted in slotted portions 46 and 41 of said frame for adjustment with respect thereto, in a usual manner, and is adjustably moved along said slotted portions to take up tension of the tread, by means of adjusting screws 48 and 49.

The front drive sprocket 3| is keyed on a transverse shaft 50 which is journaled in the tread supporting frame 21 on ball bearings 5|, 5|. A sprocket 52, keyed on the outer end of said shaft, is meshed with a drive chain 53. Said drive chain extends rearwardly from said sprocket and its upper run is trained under a tension idler roller 54, arranged to hold the tension of said chain substantially uniform during tilting movement of said tread device in one direction or another about the axis of the shaft 34. Said chain is driven at its rear end from a sprocket splined on the outer end of a transversely extending drive shaft 56 (see Figures 3 and 5). Said drive shaft is driven from the motor 2| through a difierential drive connection which will hereinafter be more clearly described as this specification proceeds.

The pivoted arm 33 is pivotally connected with the main frame ||l beneath the turntable II on a transverse shaft 6| (see Figures 6, 7 and 10). Said shaft extends through a pair of spaced transversely extending bosses 58 and 59 formed integrally with the rear end of said arm, and is mounted at its ends in spaced bosses G2, 62 depending from the rear end of a longitudinally adjustable supporting frame member 50. Said frame member is secured to the underside of the main frame III for longitudinal adjustment with respect thereto, by means of cap screws 53, 63, extending upwardly through slotted portions 64, 64 of said frame member and threaded in the underside of said main frame. An upwardly projecting longitudinally extending gib 65, extending within a downwardly opening longitudinal guide 66 formed in the bottom'of said main frame, is provided to hold said supporting frame member in alignment with said main frame during the assembling operation and during adjustment of said frame member along said main frame.

An adjusting screw 61 is provided to adjustably move said frame member along the slotted guide 66, to adjust the tension of the drive chain 53. Said adjusting screw, as hereinshown, is threaded in the forward end of the frame member and extends through a lug 69, depending from the bottom of the main frame Ill. Lock nuts HI, 10 threaded on the end of said adjusting screw are provided to adjustably move said frame member towards said lug or to permit said frame member to be moved in a direction away from said lug, it being understood that the cap screws 63, 63 are loose during the adjusting operation, and are tightened to hold said frame member in place when the chain 53 is at the proper tension.

The pivoted support arm 33 has a forwardly projecting portion 1|, which extends from the shaft 34, and has a piston rod 12 pivotally connected to its forward end. Said piston rod 12 extends from a piston I3, movable within a fluid pressure cylinder 14. Said cylinder is provided with an upwardly projecting lug I5 extending between and pivotally connected with a bifurcated connecting ear I6, projecting forwardly from the frame member 60. Fluid under pressure may be admitted to one or the other of the cylinders I4, I4 to tilt the main frame and cutter bar I'I about either thread, or may be admitted to both of said cylinders together to elevate or lower the forward end of the main frame and cutter bar about the rear steering wheels 23, 23. Fluid under pressure may also be held in said cylinders to hold the main frame and cutter bar in the various desired positions of adjustment with respect to the ground. The valve means and fluid connections from said valve means to said cylinders will hereinafter be more fully described as this speciflcation proceeds.

A guide member 19 projecting downwardly from said frame member 60, adjacent its forward end, extends within a slotted portion 80 of said forwardly projecting portion of said pivoted arm, to form a guide therefor and to aid in holding said pivoted arm from lateral movement with respect to said frame member during operation of the machine (see Figures 4 and 10).

The drive from the motor 2| to the tread devices 22, 22 includes a plural speed planetary geared reduction device BI, controlled as usual by a friction band 82, and driven from said motor through spur reduction gearing 83 (see Figures 3 and 5). Said planetar may be of any well known form and is here provided to provide a plural speed reduction drive to said tread devices so the machine may be moved along the ground at either a slow feeding speed or a fast tramming speed. A transverse shaft 84 is driven from said planetary and has a spur pinion 85 feathered thereon, which meshes with and drives a. spur gear 86 keyed on a sleeve 81, which is freely mounted on a transversely extending shaft 88. A suitable means, not shown, may be provided to slidably move said pinion 85 along the shaft 84 to disengage said pinion from or to mesh said pinion with said spur gear 86, to form a means to selectively connect said tread devices with the motor 2|.

A sprocket 93 is herein shown as being formed integral with the sleeve 81 and meshes with a drive chain 94. Said drive chain meshes with and drives a sprocket 95 on a hollow shaft 96, journaled in said main frame coaxial with the drive shaft 56 (see Figures 3 and 5). Said hollow shaft has a casing 91 of a differential secured to 'its inner end, and forms a means for driving said casing. A plurality of pinions I00, I are journaled within said casing on pins IOI, IOI. Said pinions mesh with a bevel gear I02 on the inner end of the drive shaft 56, for driving said shaft and the right-hand continuous tread device through the drive chain 53. They also mesh with a similar bevel gear I03, splined on a transversely extending shaft I04, suitably journaled in said main frame and having a sprocket I secured to its outer end. Said sprocket meshes with and drives the left-hand drive chain 53 and its associated tread device.

Brakes for the tread devices are provided on the shafts 56 and I04. Said brakes are the same for each shaft so the same part numbers will be applied to each brake and one only will herein be referred to in detail. A brake drum I01 keyed on the hub of the sprocket is adapted to be engaged by a friction band I09 (see Figure 11). Said friction band is provided with an outwardly projecting lug I I0, intermediate its ends, which is adapted to extend within a downwardly opening slotted portion III of the main frame I0. Said friction band has a connecting lug II2 extending outwardly from its upper end, which has an eyebolt II3 pivotally connected thereto. Said eyebolt depends from said lug and extends through a block II4, pivotally secured to a connecting link II5, within the sides of said connecting link. A spring H6 is interposed between said eyebolt and said block to hold said block in engagement with lock nuts H1, H1 threaded on the end of said eyebolt.

The connecting link H5 is pivotally connected at one of its ends, to a lug II 8 projecting outwardly from the end of said friction band opposite from the lug H2, and is pivotally connected at its opposite end to the lower end of a piston rod II9 extensible from a fluid pressure cylinder I20. Said cylinder is provided with an upwardly projecting lug I2I pivotally connected between the furcations of a bifurcated bracket I22, depending from the underside of said main frame. A tension spring I23 is connected between said link and the underside of said main frame, to release said friction band from said brake drum when fluid is released from said cylinder. Said friction bands may be independently applied to said brake drums, so either one or the other tread device may be held from movement, to aid the rear steering wheels 23, 23 in steering the machine as will hereinafter more clearly appear as this specification proceeds.

The rear steering wheels 23, 23 are mounted beneath the rear end of the main frame I0 in an elevated downwardly opening recess I24 formed integrally with said main frame. In the form shown, said recess is of an inverted substantially cup-like formation having a central opening therein (see Figures 12 and 13). An annular flange I26 encircles said opening and is abutted at its underside by a flange I21 of a depending hollow sleeve I20, which is secured to said annular flange by means of cap screws I30, I30. An upright bearing support I3I is rotatably mounted in the lower end of said hollow sleeve, as by an anti-friction bearing I32. Said bearing support has an operating and control shaft I33 fixed therein and extending upwardly through an antifriction bearing I 34, at the upper end of said sleeve I20.

The upright bearing support I3I has a pair of relatively short stub dead axles I35, I35 fixed therein and projecting at opposite sides thereof, just below the sleeve I29 (see Figure 13). Each of said stub axles has a rubber-tired wheel 23 rotatably mounted thereon. The axes of said stub axles are preferably inclined downwardly so that the two wheels 23, 23 are dished inwardly and approach each other at their bottom tread surfaces to provide the proper camber to said wheels. The detailed construction of said wheels and their anti-friction mounting on said stub axles are not herein shown since they are no part of my present inventipn.

The control shaft I33 has a gear sector I36 keyed to its upper end, the teeth of which mesh with a transversely extending rack I31. Retaining segments I39, I39 are secured to opposite sides of said gear sector and extend over the teeth of said gear sector and rack, to limit lateral movement of said rack with respect to said gear sector, to prevent binding between the teeth of said rack and gear sector. Said rack is secured to the outer side of a cylinder I4I, mounted on a piston rod I42 for movement therealong. Said piston rod is herein shown as having a piston I43 mounted thereon, intermediate its ends, and as being mounted at its ends in opposite walls of a housing I44, for the steering mechanism. Said piston rod is drilled along its longitudinal axis from each end thereof to points adjacent opposite sides of said piston, and is provided with ports I45, I45 opening from said drilled portions into said cylinder, to cause movement of said cylinder along said piston rod in one direction or another, upon the admission of fluid under pressure to the inside of said cylinder through either one of said ports.

The cylinder MI is manually urged in the direction of its axis, to effect steering, by means of a nut I46 on a threaded shaft I41. Said cylinder has an apertured engaging ear I48 projecting away from the gear sector I36, intermediate the ends of said cylinder, the apertured portion of which encircles the shaft I41. Another apertured ear I49 spaced from said first mentioned ear, projects away from the gear sector I36, adjacent the left-hand end of said cylinder when looking towards said gear sector, and encircles said shaft. Said ears are adapted to engage opposite sides of the nut I46. A-rod II mounted at its ends in said ears and extending through an ap'ertured portion of said nut, is provided to hold said nut from rotation, so rotation of said shaft will cause said nut and ears to move therealong. It should here be noted that the angle of the threads on said shaft is such that movement of said nut along said shaft, effected by movement of said cylinder in one direction or another, as when the steering wheels 23, 23 engage an obstruction on the ground, will cause rotation of said shaft so the feel of steering and 7 the location of the steering wheels may be felt by the operator holding the steering Wheel.

The threaded shaft I41 is journaled at one of its ends in a ball bearing I53 mounted in a bearing support cap I54, which is mounted in a wall of the steering housing I44. Said bearing is so constructed as to permit limited movement of said shaft in the direction, of its axis when thrusts are imparted to said shaft during the steering operation. The end of said shaft opposite said bearing is splined and extends through a splined hub I55 of a bevel gear I56 (see Figure Said hub of said bevel gear is herein shown as being journaled at its inner end on a ball bearing I51, mounted in a bearing support brackct I58, and at its outer end on a ball bearing I59 mounted in the steering housing I44. Said bevel gear meshes with a bevel gear I60 keyed on a longitudinal shaft I6I. Said shaft is journaled on anti-friction bearings I62, I62 mounted in a bearing support member I63, secured to a rear open portion of said housing I44. A hand wheel 10 direction or another, and correspondingly urge the cylinder MI in the desired direction, to effect turning of the wheels 23, 23 about the axis of the control shaft I33 in an obvious manner.

A valve I65, actuated in accordance with the direction of thrust of the threaded shaft I41, is provided to supply fluid under pressure through either of the ports I45, to move the cylinder I4I along the piston rod I42 in one direction or another, depending upon the direction the hand wheel I64 is turned, so said cylinder may act as a booster, to aid the steering operation. Said valve is herein shown as being a four-way piston valve, moved into one open position by end thrust of the threaded shaft I41, and moved into another open position by means of a spring I66 (see Figure 16). Said spring encircles a stem I61 projecting from the right-hand end of a Spool I68 of said valve. Said spring abuts said spool at one of its ends and abuts the shouldered end of an end chamber I69 of said valve at its opposite end. Said end chamber is formed in a detachable end cap piece I10 of said valve.

A stem I1I projects from the opposite end of the valve spool I68 and is adapted to be engaged by a ball I13 Held in a cupped end I14 of the threaded shaft I 41, so said shaft may freely ro tate without causing rotation of said spool I68 (see Figure 15). A spring I15 is interposed between the flange of a flanged sleeve I16 which engages the left-hand end of said valve spool and a Washer I11 abutting a collar I18 on said valve stem. Said spring is lighter than the spring I66 and its purpose is to serve as a locater when assembling the valve on the machine, to hold said valve stem in a position to be adjusted to said ball.

A spring I19, encircling the shaft I41 within the hub I of the bevel gear I56, is provided to move said shaft to a centered position, so the valve I will be in a neutral position when I64 on the outer end of said shaft is provided to turn said bevel gears and the threaded shaft I41, to move the nut I46 along said shaft in one there is no end thrust on said shaft. Said spring is interposed between a collar I abutting a shouldered portion I8I of said shaft, and a collar I82 held on said shaft by means of a nut I83, threaded on the end of said shaft. The collar I80 also abuts an internal shouldered portion I84 of the hub I55, to limit the distance said spring can move said shaft in a direction away from said valve so said spring will not move said shaft to the left beyond a centered position. The distance said spring can move said shaft in a direction towards said valve is limited by an externally threaded nut I85, threaded within the outer end of the hub I55, which limits movement of said shaft by said spring in a direction to the right beyond a centered position.

Fluid under pressure enters the valve I65 through a pressure passageway I86. This passageway is blocked by a land I81 of the valve spool, when said valve is in a neutral position. When the hand wheel I64 is turned in a direction to put a thrust on the threaded shaft I41 in a direction, which is to the right when looking at said valve from said hand wheel, the thrust of said shaft on the end of the valve stem I1l will move said valve spool to the right, in a position to permit fluid under pressure to pass from the pressure passageway I86 past the land I81 and a land I88 of said valve spool, out through a pressure passageway I89 to the left-hand end of the piston rod I42, and through the hollow inside of said piston rod into the left-hand side of the cylinder I4I, through the port I45. This will move the cylinder I4I to the left and will turn the wheels in a clockwise direction about the axis of the control shaft I33, to cause the machine to turn to the operator's right when travelling in a rearward direction and the operator is facing the steering wheel I64. During movement of the cylinder I4I to the left, fluid will be exhausted from the right-hand end of said cylinder through a pasageway I94 leading to the chamber of said valve, through the chamber of said valve and out of said valve to the return through a passageway I92. As soon as pressure is relieved from the steering wheel I64, end thrust on the shaft I41 will be relieved and the spring I19 will move said shaft to the left a distance sufilcient to permit the spring I66 to move said valve to a neutral position, to close the passage of fluid under pressure to said valve. When said valve is in a neutral position, fluid may flow from the left-hand end of the cylinder I4I through the passageway I89 to the valve chamber, and out of said valve chamber through passageways I90 and I9I to the return through said return passageway I92.

When the hand wheel I64 is turned in an opposite direction, the thrust on the threaded shaft I41 will be to the left. When end thrust on said shaft has moved said shaft to the left a predetermined distance, the spring I66 causing the valve spool I68 and the valve stem IN to follow said shaft, will move said valve spool to a position to permit fluid to pass through the pressure passageway I86 past the land I81 of said valve spool, and past a land I93 of said valve spool, through the passageway I94 to the right-hand end of the cylinder I 4I. This will exert a pressure on the right-hand end of the piston I43 and cylinder MI, and will tend to move said cylinder to the right to turn the steering wheels 23, 23 in a counter-clockwise direction, to cause the vehicle to turn to the operator's left, when facing the steering wheel I64,

In a contrary manner, when the vehicle is travelling along the ground and the wheels 23, 23 hit an obstruction which turns them in one direction, the ears I48 and I49 of the cylinder I4I will move the nut I46 along the shaft I41 in the direction of movement of said cylinder. This will rotatably drive said shaft and will turn the hand wheel I64 through the bevel gears I56 and I60. If the turning of said hand wheel is resisted by the operator, the thrust exerted on said shaft by said nut will be in the direction of travel of said nut, and said nut besides rotatably driving said shaft will move said shaft endwise in one direction to open the valve I65, or in another direction to permit the spring I66 to open said valve, depending upon the direction of the end thrust on said shaft, to apply fluid under pressure to the end of the cylinder I4I opposite from the direction of movement of said nut and cylinder. This will tend to automatically turn said steering wheels to their initial position and will reduce the shocks imparted to said hand wheel I64, but will still enable the operator to retain the fee] of steering.

Two valves I95 and I96 are provided to supply fluid under pressure to either or both of the brake cylinders I20, I20, to engage the friction bands I09, I09 with the drums I01, I01 and to apply the brakes of the machine. Said valves are shown herein as being variable pressure valves of the piston type and may be operated together to apply said friction bands simultaneously to hold both continuous treads from movement. or may be operated independently of ea h other, by the steering mechanism, so that either friction band ma be applied separately, depending upon the direction of turning of the machine, with a varying degree of pressure which increases as the angle of the steering wheels with respect to the longitudinal axis of the machine increases. The valve I has a plunger I91 extensible from its valve casing, which is adapted to be engaged by an arm I99 of a valve operating lever 200. In a like manner, the valve I96 has an extensible plunger 20I adapted to be engaged by an arm 202 of a valve operating lever 203. The valve operating levers 200 and 203 are pivoted for movement about a common axis on a pivotal pin 204, mounted on a member 205. Said member is mounted between said valves, for slidable movement with respect thereto, in channelled guides 206, 206, and serves to simultaneously depress said plungers I91 and 20I, to apply the brakes together, upon movement of said member in a direction away from the gear sector I36. A stop 23I depends from said member. Said stop is adapted to engage a platform 221, which forms a support for said valves, and to limit movement of said member in a direction towards the control shaft I33, to cause said member to form a fixed pivotal support for said valve operating levers, during operation of said valves by the steering mechanism, when the forces exerted on said member are towards the shaft I33. The means for manually moving said member along said guides in a. direction away from the shaft I33, to apply said brakes, will hereinafter be more clearly described as this specification proceeds.

The valve operating levers 200 and 203 extend over the top of the gear sector I36 and are adapted to be engaged by a roller 201 projecting upwardly from said gear sector and rotatably mounted on a pin 208, threaded in the web of said gear sector. When said gear sector moves in one direction, the roller 201 will engage the valve operating lever 200 and pivot said lever in a counterclockwise direction about the axis of the pin 204, to depress the plunger I91, to cause the valve I 95 to supply fluid under pressure to its respective brake cylinder I20 at pressures which increase as movement of said operating lever away from the center of the machine increases. When said gear sector moves in an opposite direction, said roller will engage the operating lever 203 and pivot said lever in a clockwise direction about the axis of the pin 204, to depress the plunger 20I and cause the valve I 96 to suppl fluid under pressure to the opposite brake cylinder I20, at pressures which increase as the angle of the wheels with respect to the longitudinal center line of the machine increases.

The pin 208 may be inserted in any one of a pluralityof spaced holes 209, 209 formed in the web of said gear sector, to change the position of the roller 201 and to vary the point at which either of tne friction bands I09 are first applied, so as to permit a certain limited amount of turning movement of the steering wheels before applying either friction band, if desired, and so as to varythe point of maximum pressure admitted to either fluid cylinder I20. Moving said roller outwardly on a radius extending along the longitudinal center line of said gear sector will cut down the dead angle at which there will be no pressure passing through the valves I95 or I96 and will increase the maximum pressure applied to the respective brake band. The dead angle 13 and maximum pressure may also be varied by changing the size of said roller.

The'valves I95 and I96 are of the same construction so one only need herein be shown and described in detail. The plunger I91 of the valve I95 is provided with a shouldered portion 2I0 within the chamber of the valve, which limits movement of said plunger in an outward direction, and which is adapted to be engaged by a compression spring 2 (see Figure 18). The opposite end of said spring is seated in a seat 2I2, loosely mounted on the end of a. valve spool 2I3. Pressure is adapted to enter the chamber of said valve between a pair of spaced lands 2 and 2I9 of said valve spool, through a pressure passageway 2|I6.

As the plunger I91 is depressed by the arm I99 of the valve operating lever 200, the spring 2I'I will move the valve spool 2 I3 to a position to perunit fluid to pass into an annular groove 2 I1 formed in the valve chamber, and through cross drilled passageways 2I0 in said valve spool to the hollow inside of said valve spool, and out of said valve to the brake cylinder I20 through a passageway 2I9. Said valve spool is drilled to the right from its hollow inside portion, to connect said hollow inside portion with cross drilled passageways 229, 229 in the space between the land 2M and a land 22I on the right-hand end of said valve spool, to permit fluid to be released through a return passageway 222. I

As the spring 2i I is displaced to the left by the plunger I91, the force exerted by said spring on the valve spool 2i 3, to move said valve spool to the left, will be increased. Thus the pressure against the left-hand end of said valve spool, required to move said valve spool to the right to release pressure through the hollow inside of said valve spool, will also be increased. This will result in an increase in pressure passing through the passageway 2 I9 up to the maximum pressure entering the valve through the passageway 2I6.

As the gear sector I36 is moved in a clockwise direction, the spring 2H will move the plunger I99 to the right to follow the arm I99. As tension of the spring 2i 8 decreases due to movement of said plunger to the right, or as pressure in the passageway 2I9 increases to an amount which is greater than the pressure represented by the displacement of said spring, pressure on the lefthand end of said valve spool will move said valve spool to the right, to permit the release of fluid through the cross drilled passageways 229, through the return passageway 222, leading to the low pressure side of an accumulator 229, resulting in a gradual decrease in pressures in the passageway 2 I 9, until pressure in said passageway balances the pressure exerted by said spring.

It should here be understood that during turning of the wheels 23, 23 for steering, when either of the plungers I91 or 29f is depressed to supply fluid to the respective brake cylinder at a maximum pressure, and it is desired to apply the other brake so the two brakes will be applied simultaneously, tostop travel of the machine, or to hold it from movement, that said lungers must be permitted to travel a distance greater than the normal distance of travel required to displace their springs the required distance to supply the maximum pressure supplied by the accumulator of the fluid system to the brake cylinders I20. I20. This is necessary in order that the member 205 may apply the two brakes when one is already applied, by movement in a direction away from the control shaft I33, to simultaneously depress 14 the plungers I91 and 20I In the present instance the plungers I91 and 2M have a travel of twice the distance necessary to supply the maximum pressure supplied by the accumulator of the fluid system to the respective brake cylinder I20.

Referring now to the means for rectilinearly moving the member 205 in the channel] guides 206, 206, to simultaneously apply the two friction bands I09, I09, the inner sides of the valve operating levers 200 and 203 engage a reaction member 224, when the wheels 23, 23 extend parallel to the longitudinal axis of the machine (see Figure 14). Said reaction member is mounted on the upper end of the control shaft I33 and limits movement of said arms inwardly towards each other. The member 205 is rectilinearly moved along the guides 206, 206 in a direction to depress the plungers I91 and 20I of the valves I95 and I96, bymeans of a lever arm 225 mounted at its lower end on a transverse rock shaft 226, which is pivotally mounted on the underside of the platform 221 (see Figure 19). Said lever arm has a slotted upper end which extends upwardly through a slotted portion of said platform and has slidable engagement with a pin 22 9, mounted at its ends in opposite sides of an open portion 230 of the member 205. A rocking arm 232 is keyed on the end of said rock shaft 226 and is connected with a rocking arm 233 by means of a link 234. Said rocking arm 233 is pivotally mounted on the elevated portion I24 of the main frame I0, adjacent the right-hand end of the piston rod I42, on a pivotal pin 235, and has a rearwardly projecting arm 236 formed integrally therewith. A link 231, pivotally connected to said last mentioned arm, extends transversely of the machine through a guide 238. Said link has an upwardly :bent hand grip on its end for operating said rocking arms and applying the brakes by moving the member 205 rectilinearly along the channelled guides 206, 296 in a direction away from the control shaft I33, so as to bodily move the valve operating levers 209 and 203 towards the valves I95 and I96, to depress the respective plungers I91 and 29L Movement of said'link in either direction is limited by means of a pair of stops 239, 299.

Referring now to Figure 21, showing the dia-' gram of the fluid system for supplying fluid to the several operating cylinders of the machine, a fluid pump 243 is provided to supply fluid under pressure to the system. Said pump is driven from the motor 2 I, which also serves to turn the turntable I I and to'drivethe continuous tread devices 22, 22. The drive connection from said motor to said pump is not herein shown or describ d since it is no part of my present invention. Said pump is connected with the low pressure side of the accumulator 223 by means of a pipe 244 connected with a reversing valve 245. The low pressure side of said accumulator serves as a fiuid storage tank, for the system in a manner well known to those skilled in the art. Pipes 246 and 241 lead from opposite ends of said reversing valve to opposite sides of said pump, one of said pipes acting as a suction pipe and the other of said pipes acting as a pressure pipe, depending upon the direction of rotation of said pump.

The reversing valve 245 is only herein shown diagrammatically since it is no part of my pres nt invention, and is provided to reverse the passage of fluid to the pump 243 from one side of said pump to the other, so said pump will always supply fluid under pressure to the system regardless of its direction of rotation, and replaces the usual check valves provided on reversible pumps. Said valve includes a spool 249 movable in the chamber of said valve and so arranged as to permit fluid under pressure to pass from said pump through the pipe 246 or the pipe 241, to a ressure pipe I, depending upon the direction of rotation of said pump. Fluid under pressure passing through either of the pipes 246 or 241 engages an end of said spool and moves said spool to a position to connect the pipe 244 with the suction side of said pump through either of the other of said pipes 246 or 241. The pressure pipe 25I connects the reversing valve 245 with an unloading or relief valve 252. Said relief valve may be of any well known form and its relief or low pressure side is connected with the tank or low pressure side of the accumulator 223 by means of a pipe 253. Said valve is connected with the high pressure side of said accumulator, for supplying fluid under pressure thereto, by-means of 8. pipe 254.

A pressure pipe 259 connects the pipe 254 and the high pressure side of the accumulator 223 with two valves 266, 260. Said valves are herein shown as being independently operable four-way piston type valves connected with opposite ends of the cylinders 14, 14, to supply fluid under pressure to either the head or piston rod ends of said cylinders, so said cylinders may elevate or lower the forward end of the main frame I6 and may tilt said main frame about one tread 22 or the other, and may also hold said main frame in the desired elevated or tilted position.

A pressure line 26I leads from the pipe 254 and the high pressure side of the accumulator 223 to the pressure passageway I86 of the steering valve I 65, to supply fluid under pressure thereto. A return pipe 262 leads from the return passageway of said valve to the low pressure side of said accumulator, to return fluid thereto. A pressure pipe 263- connects the pressure port I69 of said valve with the left-hand end of the piston rod I42. A pressure pipe 264 connects the pressure port I94 of said valve with the right-hand end of said piston rod.

The brake valve I96 is connected with the pump 243 and high pressure side of the accumulator 223 by means of a pressure pipe 265 leading from the pressure pipe 254. A pressure pipe 266 connects said pipe 265 with the pressure side of the valve I96. A return pipe 261 connects the valve I95 with the low pressure side of said accumulator. A return pipe 268 connects the valve I96 with the low pressure side of said accumulator.

Pressure pipes 269 and 216 connect said valves' with the respective brake cylinders I20, I20.

A drain pipe 21l connected with the pipe 261 is provided to carry fluid which may leak by the limited in the appended claims.

I claim as my invention:

1. In a kerf-cutting machine, a main frame, a cutter chain carrying cutter bar pivotally mounted at the front of said main frame for movement about a vertical axis and projecting forwardly beyond said main frame to cut a kerf across the 16 front of and to each side thereof, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and withdrawing it from a coal face and forming a stable support means for said outter bar when disposed to either side of said main frame and during cutting across the forward end of said main frame, including two relatively short laterally spaced continuous tread devices at the forward end of said main frame at opposite sides thereof, steering wheel means supporting the rear end of said main frame, said steering wheel means being spaced a substantial distance from said tread devices, and said tread devices being so located with respect to the center of gravity of the machine that the major portion of the load during cutting and transportation of the machine will be taken on said continuous tread devices and the load on said steering wheel means will only be sufiicient to give said steering wheel means traction to assist said tread devices in steering the machine.

2. In a kerf-cutting machine, a main frame, a cutter chain carrying cutter bar pivotally mounted at the front of said main frame for movement about a vertical axis and projecting forwardly beyond said main frame to cut a kerf across the front of and to each side thereof, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and withdrawing it from a coal face and forming a stable support means for said cut ter bar when disposed to either side of said main frame and during cutting across the forward end of said main frame, including two relatively short laterally spaced continuous tread devices at the forward end of said main frame at opposite sides thereof, steering wheel means supporting the rear end of said main frame, said steering wheel means being spaced a substantial distance from said tread devices, and the center of gravity of the machine being within the limits of said tread devices to distribute the weight between said steering wheel means and said tread devices so that a major portion of the load during cutting and transportation will be taken on said tread devices, and the load on said steering wheel means will only be sufficient to give said steering wheel means traction to assist said tread devices in steering the machine.

3. In a kerf-cutting machine, a main frame, a turntable at the front of said main frame, a cutting element mounted on said turntable and projecting beyond the forward end thereof and ineluding a cutter chain carrying cutter bar supported in front of said main frame to cut a kerf across the front of and to either side of said main frame, adjacent the mine bottom, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and withdrawing it from a coal face and forming a stable support means for said outter bar when disposed to either side of said main frame and during cutting across the forward end of said main frame, including two laterally spaced continuous tread devices at the forward end of said main frame at opposite sides thereof, steering wheel means supporting the rear end of said main frame, a separate transverse pivotal mounting for each of said tread devices on said main frame disposed intermediate the ends of said tread devices, the distance from the pivotal axes of said transverse pivotal mountings to the forward ends of said tread devices being less than the distance from the center of gravity of the asvasaa ter bar, means for propelling said main frame about the mine floor and for feeding said cutter bar longitudinally into and withdrawing it from a coalface including two laterally spaced continuous tread devices and ground engaging support and steering means spaced rearwardly of said tread devices for supporting and steering the rear end of said main frame, and independent supporting connections between said tread devices and said main frame including a separate supporting arm for each tread device, transverse pivotal connections between said arms and said main frame, a transverse pivotal supporting connection between each arm and an associated tread device, and means connected between said main frame and said arms for holding said arms from pivotal movement with respect to said main frame or for independently or simultaneously pivoting said arms about their axes of pivotal connection to said main frame, to tilt said cutter bar about transverse or longitudinal axes.

5. In a kerf-cutting machine, a main frame, a cutting element mounted on said main frame and including a projecting cutter chain carrying outter bar, means for propelling said main frame about the mine floor and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including two laterally spaced continuous tread devices and ground engaging support and steering means spaced rearwardly of said tread devices for supporting and steering the rear end of said main frame, and independent supporting connections between said tread devices and said main frame including a separate supporting arm extending along each tread device, a transverse pivotal connection between one end of each of said arms and said main frame, a transverse pivotal connection between each arm and an associated tread device, and extensible means connected between the free ends of said arms and said main frame for holding said arms stationary with respect to said main frame or for independently or simultaneously pivoting said arms about their axes of pivotal connection to said main frame, to tilt said cutter bar about transverse or longitudinal axes.

6. In a kerf-cutting machine, a main frame, a cutting element mounted on said main frame and having a projecting cutter chain carrying cutter bar, means for propelling said machine about the mine floor and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including two laterally spaced continuous tread devices and ground engaging support and steering means spaced rearwardly of said tread devices for supporting and steering the rear end of said main frame, and a supporting connection between said tread devices and said main frame including a separate pivoted arm extending along the inside of each tread device, transverse pivotal connections between the rear ends of said arms and said main frame, transverse pivotal connections between said arms and said tread devices,

and extensible means connected between said mainframe and said arms for holding said arms from pivotal movement with respect to said main 18 frame, or for pivoting said arms about their axes of pivotal connection to said main frame. to tilt said cutter bar about transverse or longitudinal axes.

7. In a kerf-cutting machine, a main frame, a cutting element mounted on said main frame and having a projecting cutter chain carrying cutter bar, means for propelling said machine about the mine floor and for feeding saidcutter bar longitudinally into and withdrawing it from a coal face including two laterally spaced continuous tread devices and ground engaging support and steering means spaced rearwardly of said tread devices for supporting and steering the rear end of said main frame, and a supporting connection between said tread devices and said main frame including a separate pivoted arm extending along the inside of each tread device. transverse pivotal connections between the rear ends of said arms and said main frame, transverse pivotal connections between said arms and said tread devices intermediate the ends of said arms, and extensible means connecting the'forward ends of said arms with said main frame, for holding said arms from pivotal movement with respect to said main frame or for pivoting said arms about their axes of pivotal connection to said main frame, to tilt said main frame and cutter bar about transverse or longitul axes.

8. In a kerf-cutting machine, a main frame, a cutting element mounted on said main frame and having a projecting cutter chain carrying cutter bar, means for propelling said machine about the mine floor and for feeding said cutter bar longigg tudinally into and withdrawing it from a coal face including two laterally spaced continuous tread devices and ground engaging support and steering means spaced rearwardly of said tread devices for supporting and steering the rear end of do said main frame, and a supporting connection between said tread devices and said main frame including a separate pivoted arm extending along each tread device, transverse pivotal connections between the rear ends of said arms and said main frame, transverse pivotal connections between said arms and said tread devices intermediate the ends of said arms, means for limiting pivotal movement of said tread devices with respect to said arms, and extensible devices connecting the forward ends of said arms with said main frame for holding said arms from pivotal movement with respect to said main frame or for pivoting said arms about their axes of pivotal connection to said main frame, said extensible means being s; independently operable to tilt said cutter bar about transverse or longitudinal axes.

9. In a kerf-cutting machine, a main frame, a cutting element mounted on said main frame and having a projecting cutter chain carrying cutter w bar, means for propelling said machine about the mine floor and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including two laterally spaced continuous tread devices and ground engaging support and steering means spaced rearwardly of said tread devices for supporting and steering the rear end of said main frame, and a supporting connection between said tread devices and said main frame including a separate pivoted arm extending along each tread device, transverse pivotal connections between said arms and said .main frame, transverse pivotal connections between said arms and said tread devices intermediate the ends of said arms, means for limiting pivotal movement of said tread devices with respect to said arms, and extensible devices connecting said arms with said main frame, for holding said arms from pivotal movement with respect to said main frame or for pivoting said arms about their axes of pivotal connection to said main frame, said extensible devices each including a fluid pressure cylinder having a piston rod extensible therefrom, and valve means for controlling the admission and release of fluid under pressure to and from said cylinders, independently of each other, to tilt said cutter bar about transverse or longitudinal axes and to hold said cutter bar in fixed relation with respect to said arms.

10. In a kerf-cutting machine, a main frame, a

turntable on said main frame, a cutting element mounted on said turntable and including a projecting cutter chain carrying cutter bar, said turntable being adapted to feed. said cutter bar across a coal face to cut a kerf therein, and means for supporting and propelling said machine about the mine floor and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including centrally disposed rubbertired steering wheel means at the rear end of said main frame and forming a support for the rear end thereof, and two independently mounted laterally spaced continuous tread devices at opposite sides of the forward end of said main frame forming a supporting and propelling means therefor, said tread devices extending from the forward end of said turntable rearwardly beyond the pivotal axis thereof to form a stable support for said main frame and to support said cutter bar in the same cutting plane, when said turntable is turned to position said cutter bar to either side of said main frame, a separate arm for each tread device pivotally connected to said main frame, for supporting said tread devices to follow an uneven mine bottom, and independently operable extensible means connected with said arms for hold ing said arms stationary or for pivoting one or both of said arms with respect to said main frame, for tilting said main frame and cutter bar with respect to the ground.

11. In a kerf-cutting machine, a main frame, a turntable on said main frame, a cutting element mounted on said turntable and including a projecting cutter chain carrying cutter bar, said turntable being adapted to feed said cutter bar across a coal face to cut a kerf therein, and means for supporting and propelling said machine about the mine floor and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including a rubber-tired steering wheel forming a support for the rear end of said main frame and two laterally spaced continuous tread devices at opposite sides of the forward end of said main frame forming a supporting and propelling means therefor, said tread devices extending from the forward end of said turntable rearwardly beyond the pivotal axis thereof to form a stable support for said main frame and to support said cutter bar in the same cutting plane, when said cutting element is positioned to either side thereof, and an adjustable supporting connection between said tread devices and said main frame including a separate pivoted arm for each tread device transversely pivoted to said truck adjacent its rear end and having a treaddevice pivoted thereto intermediate its ends, and separate independently operable extensible means pivotally connected between said main frame and the forward ends of said arms for holding said arms from pivotal movement with respect to said 20 4 main frame, or for tilting said main frame about transverse or longitudinal axes, to change the angle of said cutter bar with respect to the ground.

12. In a kerf-cutting machine, a main frame, a cutter chain carrying cutter bar projecting from said main frame, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including two laterally spaced continuous tread devices forming a support for the forward end of said main frame, a motor on said main frame, a drive connection from said motor to said tread devices, a centrally disposed rear rubber tired steering wheel forming a support for the rear end of said main frame] means for turning said wheel for steering the machine, individual braking means for each of said tread devices, and connections between said steering means and said braking means, for applying an increasing pressure to either one of said braking means upon turning movement of said steering wheel, to retard travel of and to brake the tread device on the side of said main frame towards which it turns, said connections being arranged to increase the braking pressure of said braking means a predetermined amount as the degree of turning of said steering wheel away from the longitudinal axis of the machine increases and including a variable pressure fluid valve operatively connected with said steering wheel to supply fluid under pressure to said braking means upon turning movement of said steering wheel.

13. In a kerf-cutting machine, a main frame, a cutter chain carrying cutter bar projecting from said main frame, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and.

withdrawing it from a coal face including two continuous tread devices spaced at opposite sides of said main frame adjacent the forward end thereof, and two closely spaced centrally disposed rear steering wheels forming a support for the rear end of said main frame, means for turning said wheels together for steering the vehicle including an upright shaft and a steering member connected with said shaft for turning said shaft, a motor on said main frame, a drive connection from said motor to said tread devices, including a difierential having driving connection with said tread devices, individual braking means for each of said tread devices, and a plurality of variable pressure fluid valves operatively connected with said steering member for applying said braking means to the tread device about which said main frame is turning, with a pressure which increases as the angle of said steering wheels with respect to the longitudinal axis of the machine increases.

14. In a kerf-cutting machine, a main frame, a cutter chain carrying cutter bar projecting from said main frame, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including two continuous tread devices spaced at opposite sides of said main frame, adjacent the forward end thereof, individual fluid operated braking means for each of said tread devices for braking said tread devices independently or simultaneously of each other, means for driving said tread devices so arranged as to permit either of said tread devices to be stopped while the other continues to travel, upon application of one of said braking means, two closely spaced centrally disposed rear steering wheels forming a support for the rear end of said main frame, a steering member for turning said wheels for steering, and means operatively connected with said steering member for applying said braking means to the tread device about which said main frame is turning, with a pressure which increases as the angle of said steering wheels with respect to the longitudinal axis of the machine increases, including two variable pressure fluid valves, fluid connections from said valves to said braking means, for applying said braking means, and an operative connection from said steering member for operating either of said valves depending upon the direction of turning movement of said steering member.

15. In a kerf-cutting machine, a main frame, a

cutter chain carrying cutter bar projecting from said main frame, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including two continuous tread devices spaced at opposite sides of said main frame, adjacent the forward end thereof, individual fluid operated braking means for each of said tread devices for braking said tread devices independently or simultaneously of each other, means for driving said tread devices, said driving means being so arranged as to permit said braking means to be applied independently of each other, two closely spaced. centrally disposed rear steering wheels forming a support for the rear end of said main frame, a steering member for turning said wheels for steering, two variable pressure fluid valves, each of said valves being adapted to have connection with one of said braking means for operating said braking means, a separate operating lever for each of said valves, and an engaging member on said steering member, adapted to have engagement with either one or the other of said operating levers, depending upon the direction of turning movement of said steering wheels, for operating said respective valve to supply fluid to its respective braking means at gradually increasing pressures as said wheels turn away from the longitudinal centerline of the machine.

16. In a kerf-cutting machine, a main frame, a cutter chain carrying cutter bar projecting from said main frame, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including two continuous tread devices spaced at opposite sides of said main frame, adjacent the forward end thereof,,individual fluid operated braking means for each of said tread devices for braking said .tread devices independently or simultaneously of each other, means for driving said tread devices,

said driving means being so arranged as to permit said braking means to be applied independently of each other, two closely spaced centrally disposed rear steering wheels forming a support for the rear end of said main frame, a steering member for turning said wheels for steering, two variable pressure fluid valves, each of said valves being adapted to have connection with one of said braking means, for operating said braking means, a separate operating lever for each of said valves,

a common support for each of said levers, an

engaging member on said steering member, adapted to have engagement with either one or the other of said operating levers depending upon the direction of turning movement of said steering wheels, a reaction member adapted to limit movement of said operating levers towards each other, and means for rectilinearly moving said support for operating said valves and applying said brakes together.

17. In a kerf-cuttlngmachine, a main frame, a cutter chain carrying cutter bar projecting from said main frame, and means for supporting said main frame for movement about the ground and for feeding said cutter bar longitudinally into and withdrawing it from a coal face including two continuous tread devices spaced at opposite sides of said main frame, adjacent the forward end thereof, individual fluid operated braking means for each of said tread devices for' braking said tread devices independently or simultaneously of each other, means for driving said tread devices, said driving means being so arranged as to permit said braking means to be applied independently of each other, two closely spaced centrally disposed rear steering wheels forming a support for the rear end of said main frame, a steering member for turning said wheels for steering, two variable pressure fluid valves for controlling operation of said braking means, each of said valves having a depressible plunger arranged so the pressure passing through its respectivev valve will increase as said plunger is depressed, a separate operating lever having engagement with each of said plungers, for depressing said plungers, a common support for each of said operating levers, an engaging member on said steering member adapted to have engagement with either one or the other of said operating levers to depress either one or the other of said plungers and apply either one or the other of said braking means with an increasing pressure as said steering wheels turn away from the longitudinal center line of the machine, a reaction member adapted to limit movement of said operating levers towards each other, and means for rectilinearly moving said pivotal support for said operating levers, for causing said operating levers to depress said plungers together to apply both of said brakes, each of said plungers having a greater travel than that necessary to cause the maximum amount of pressure to pass through its respective valve, to permit the application of the two brakes, when said steering wheels are turned in one extreme position or another.

18. In a kerf-cutting machine, a main frame, a cutter chain carrying cutter bar projecting from said main frame, and means for supporting said main frame for movement about the ground and for feeding-said cutter bar longitudinally into and withdrawing it from a coal face including two continuous tread devices spaced at opposite sides of said main frame, adjacent the forward end thereof, two closely spaced steering wheels forming a support for the rear end of said main frame, a steering member for turning said wheels for steering, individual fluid operated braking means for each of said tread devices for braking said tread devices independently or simultaneously of each other, means for driving said tread devices, sa d driving means being so arranged as to permit either of said tread devices to be stopped upon application of one of said braking means while the other tread device continues to be driven, two variable pressure fluid valves, each of said valves be ng adapted to have connection with one of said braking means, for operating said braking means, a se arate pivoted operating lever for each of said valves, and an engaging member on said steering member, adapted to have engagement with either one or the other of said operating levers, depending upon the direction of turning movement of said steering wheels, for operating said respective valve'to supply fluid to its respective braking means at gradually increasing pressures as said wheels turn away from the longitudinal center line of the machine, said engaging member being adapted to be positioned at various locations on said steering member, for varying the point at which pressure is initially applied to said braking means and'for varying the point at which maximum pressure is applied to said braking means.

19; In combination with a self-propelled vehicle having continuous tread traction devices at opposite sides thereof, individual fluid operated braking means for each of said tread devices,

- for braking said tread devices independently or simultaneously of each other, power means for driving said tread devices, said driving means being so arranged as to permit the application of one braking means while driving the other tread device for steering the vehicle, two variable pressure fluid valves for operating said braking means, a separate operating lever for each of said valves, a member movable rectilinearly of said valves and having said levers pivotally mounted thereon, a pivotally movable steering member, means on said steering member engageable with either of said operating levers, for operating either of said valves, depending upon the direction of pivotal movement of said steering member, means for limiting pivotal movement of said operatinglevers in one direction, and means for moving said support member for said operating levers with respect to said means for limiting pivotal movement of said operating levers, for simultaneously operating each of said valves and applying said' brakes together, said means being operable to open one of said valves to apply one of said brakes when the other of said valves has been opened and its respective brake has been applied by the turning of said steering member.

20. In combination with a self-propelled ve: hicle having continuous\tread traction devices at opposite sides thereof, individual fluid operated braking means for each of said treadiievices, for braking said tread device's independently or simultaneously of each other, power means for driving said tread devices, said driving means being so arranged as to permit the application of one braking means while driving the other tread device for steering the vehicle, two piston type variable pressure fluid valves for controlling operation of said braking means, each of said valves including a' valve block and a plunger depressible therein for moving said valve to a position to permit fluid under pressure to pass therethrough at pressures which increase as said plunger is depressed within the block of said valve, a separate pivoted operating lever having engagement with each of said plungers for depressing said plungers, a member mounted for slidable movement with respect to said valve blocks and having said operating levers pivotally mounted thereon, a pivoted steering member, an engaging member on said steering member adapted to have engagement with either of said operating levers, for operating either of said valves and their respective brakes upon movement of said steering member in one direction or another, means for limiting movement of said operating levers in one direction, and means for moving said support member for said operating levers in a direction parallel to the axes of said plungers, to cause said operating levers to simultaneously depress said plungers to apply said brakes together, said plungers having a' travel greater than is necessary 24 to open their respective valves for the passage of fluid under pressure therethrough, so said support member may apply one of said brakes, by opening its respective valve when the plunger of said other valve is depressed to permit maximum pressure to pass through its respective valve.

21. In combination with a self-propelled vehicle having continuous tread traction devices at opposite sides thereof, individual fluid operated braking means for each of said tread devices, for braking said tread devices independently or simultaneously of each other, power means for driving said tread devices, said driving means being so arranged as to permit the application of one braking means while driving the other tread device, for steering the vehicle, two piston type variable pressure fluid valves for controlling operation of said braking means, each of said valves including a valve block and a plunger depressible therein for moving its valve to a position to permit fluid under pressure to pass therethrough at pressures which increase as said plunger is depressed within the block of said valve, a separate pivoted operating lever having engagement with each of said plungers, for depressing said plungers, a support member for said levers mounted between said valve blocks for slidable movement with respect thereto and having said operating levers pivotally mounted thereon, a steering member, an engaging member on said steering member adapted to have engagement with either one of said operating levers, for operating either of said valves and its respective brake upon movement of said steering member in one direction or another, means for limiting pivotal movement of said operating levers in a direction opposite to their direction of movement when depressing their respective plunger, and means for rectilinearly moving said support member between said valves, to move said operating levers towards said valve blocks for causing said operating levers to apply said brakes together.

22. In combination with a self-propelled vehicle having continuous tread traction devices at opposite sides thereof, individual fluid operated braking means for each of said tread devices, for braking said tread devices independently or simultaneously of each other, power means for driving said tread devices, said driving means being so arranged as to permit the application of one braking means While driving the other tread device for steering the vehicle, two piston type variable pressure fluid valves for controlling operation of said braking means, each of said valves including a valve block and a plunger depressible therein for moving its valve to a position to permit fluid under pressure to pass therethrough at pressures which increase as said plunger is depressed within the block of said valve, a separate pivoted operating lever having engagement with each of said plungers for depressing said plungers, a support member for said plungers mounted between said valve blocks for slidable movement with respect thereto and having said operating levers pivotally mounted thereon, a steering member, an engaging member on said steering member adapted to have engagement with either one of said operating levers, for operating either of said valves and its respective brake upon movement of said steering member in one direction or another, means for limiting pivotal movement of said operating levers in a direction opposite to their direction of movement when depressing their respective plunger, and means for rectilinearly moving said support member between 

